WASHINGTON – The situation in Iraq is reaching a “critical point,” said Sen. Trent Lott, the Senate’s second-ranking Republican – as President Bush begins a new round of diplomacy to try to stanch the bloody conflict there.

“I think the circumstances have to change . . . We’re reaching a critical point,” said Lott. “I think the president, the vice president and the administration, the commission that’s working on this issue know that. Do they know that in Iraq? And that’s what has got to be determined.”

After days of bloody assaults and reprisals among rival religious sects in Baghdad, President Bush prepared for a trip to Europe and the Middle East on Monday to enlist allies to find a way forward. Leading members of Congress called on the president to lean on the fledgling Iraqi government to produce results.

Bush planned to visit Estonia and then Latvia for a NATO summit. He then heads to Jordan to meet with Iraqi President Nouri al-Maliki, who is coming under fire in Washington and from his own people for failing to stem the chaos in his country.

Jordan’s King Abdullah told ABC’s “This Week” yesterday, “The difficulty that we’re tackling with here is, we’re juggling with the strong potential of three civil wars in the region, whether it’s the Palestinians, that of Lebanon or of Iraq.”

Sen. Richard Durbin (D-Ill.), the Senate’s second-ranking Democrat, said it was “past time” for President Bush to give Maliki an ultimatum to force a solution.

“When you consider the fact that we have given basically a blank check to this Iraqi government . . . I don’t think that creates an incentive on the part of the Iraqis to stand up and defend their own country,” he said, also speaking on “This Week.”

Maliki is already under fire from some of his own people. Yesterday, his motorcade was stoned by a crowd of Shiites when he visited the notorious Sadr City slum to pay respects to 200 people who were killed in last week’s bloody attack there.

The NATO summit is expected to focus on Afghanistan, where the Taliban has been escalating attacks on the U.S.-backed government.

Events there “are reaching a critical juncture,” said retired Air Force Gen. Joseph Ralston, former NATO Supreme Allied Commander. “A military failure in Afghanistan would be catastrophic for the alliance.”

Bush is awaiting recommendations by the Iraq Study Group, headed by former Secretary of State James Baker III and Democratic Rep. Lee Hamilton of Indiana, about whether to withdraw troops or perhaps even send more to impose control on the situation.

Sen. John Cornyn (R-Texas) called for sending an additional 20,000 to 50,000 troops to Iraq to disarm militias and secure hostile areas. Sen. Jack Reed (D-R.I.), appearing with Cornyn on CNN’s “Late Edition,” responded that “the prospect of a magic bullet with just more troops, I don’t think is there.”